Stabilization of vat dye leucos at



Patented Oct. 5, 1954 UNITED STATES ATENT OFFICE STABILIZATION OF VAT DYE LEUOOS AT HIGH TEMPERATURE WITH COBALT COMPOUNDS No Drawing. Application February 8, 1951, Serial No. 210,101

8 Claims.

This invention relates to an improved process of dyeing with vat dyes at high temperatures.

In the past, high temperature dyeing, which has many advantages, has been impossible with many vat dyes because the leuco compounds have been sensitive to decomposition at the elevated bath temperatures resulting in dull, weak dyemgs.

In the co-pending patents of J. M. Mecco, Patents 2,548,543 and 2,548,544, April 10, 1951, and Patent 2,576,846, November 27, 1951 there have been described processes of vat dyeing at higher temperatures with certain assistants which have exerted an oxidation buffering action on the leuco compounds of the particular vat dyes to which these inventions related, and which were sensitive to over-reduction in the dye bath to a point where reoxidation to the final dyestuff no longer took place, or else took place too slowly to be completed in the ordinary dyeing time. The assistants were not solely oxidizing agents because other compounds that are strong oxidizing agents, such as certain nitrates, did not perform the same function.

With respect to certain pyranthrone and halogenated pyranthrone dyes, the same assistants permitted high temperature dyeing without adverse effect on shade and strength, although the leuco compounds of these pyranthrone dyes are not sensitive to over-reduction. The mechanism, therefore, in this case, involved factors which probably have nothing to do with an oxidation buffering effect. These dyeing processes are described and claimed in the J. M. Mecco copending Patents 2,548,545 and 2,548,546, April 4, 1951, and 2,576,847, November 27, 1951.

According to the present invention, we have found that an entirely different type of vat dyeing assistant, namely, compounds of cobalt, prevent decomposition and dulling of shade in the high temperature dyeing of vat dyes which ordinarily cannot be dyed at elevated temperatures. The way the cobalt compounds aifect the dyeing process is not as yet understood, although it is, clear that the oxidation buffering action which is undoubtedly a factor in the mechanism of the processes described in the Mecco patents above, is not a deciding factor because the nature of the cobalt compound does not materially aifect its action in the dye bath. In fact, many compounds of other metals known to be oxidizers do not exhibit the beneficial effects obtained with the compounds of cobalt. Although, as stated above, the exact behavior of the cobalt compounds in the vat dyeing process is not known and, therefore, the present invention is not intended to be limited to any theory of action, it seems consistent with the behavior of the dyeings that the cobalt compounds may have some effect on the reducing agent in the vat dye bath, possibly transforming the sodium hydrosulfite to a cobalt compound or to a cobalt complex. Although this theory of action of the cobalt compounds is advanced as a possibility, it should be understood that this is not a property which is shared by all polyvalent metals and appears to be peculiar to cobalt alone. It is therefore also possible that other factors are involved. In any event, it is definitely known that the cobalt compounds behave similarly with substantially all of the vat dyes, improving several dyes which do not become over reduced when dyed at high temperatures. In addition, the nature of the cobalt compound does not appear to make any difference in the nature of improvement obtained. It is evident that it is the presence of the element cobalt itself which is effecting the improved results.

The cobalt compounds probably are not catalysts in the ordinary sense of the word. That is to say, they cannot be used in amounts so small as to preclude their entering in to the reaction as reagents. As little as of an ounce of cobalt content per gallon of dye bath, however, effects a marked improvement in shade and strength when used in a high temperature dye bath with dyes that are sensitive to heat and tend to decompose when dyed under those conditions. Amounts of cobalt compound greater than 4, of an ounce per gallon generally give improved re sults, optimum results being obtainable in the range of from to ounce per gallon. Larger amounts of cobalt compound do no particular harm to the dye, but as no corresponding improvement results, there is no point in going beyond about 1 ounce per gallon. The above range is given for a five percent dyeing. When less concentrated dye baths are used in some of the weaker shades, optimum results are obtainable with a little less of the cobalt compound than required for very strong shades. In general, the amount of cobalt compound to be used is not critical. This is a practical operating advantage because it is not necessary to exert a criti cal control in the dyeing. Also, the fact that varying amounts of cobalt compound may be used permits incorporating a sufilcient amount of cobalt compound with the dyestuff itself which, in certain cases, represents an improved form for marketing.

Example 1 A dye bath was prepared withone part of a commercial dye paste of the blue vat dye having Color Index No. 1113, 390 parts of water, 12.5 parts of 30 B. sodium hydroxide, 3 parts of sodium hydrosulfite, and 5 parts of a 5% aqueous solution of cobaltous chloride. The. dye

was reduced in the bath: by heatingv at 90? C. whereupon a cotton skein. to. the amount of120 parts was entered and dyed forBO minutes at the same temperature with intermittent stirring. As: the dyeing proceeded, sodium? hydroxide and:

sodium hydrosulfite were addedawhen needed to maintain the alkaline-reducing; condition as determined by spotting on phenolphthalein and Vat Yellow G test papers. Theskein was then removed from the-bath,.oxidized, thoroughly soaped at the boil, rinsed and dried. It was dyed a bright blue shade.

A control dyeing was effected under identical conditions except that the cobalt compound'wasnot present. The shade'was muchweaker ands duller.

Eawmplev 2 i.-

A seriesof dyeings of 5% of the blue dye of Example lwas made on cotton skeinsat 93 C; Each skein was of the same weight as in Example 1, and each dye bath of the same volume, containing 1 ounce per gallon of sodium hydroxide and also one ounce per gallon of sodium hydrosulfite. To the various baths there were added different amounts of cobaltous chloride as is shown. below:

#1.None: (Control) #2% oz. per gallonof .CC12-6H2O oz. per. gallon: orcoolz- 61 120: #6 /12 oz. per gallon of C0Cl2' fiHzO. #7- oz. per gallon of C0C12 6H2O #8-% oz. per gallonof CoGlz-SI-IzO:

In each case the dye was reduced andthecotton" skein then entered and dyed for 30"minutes at 93 C. adding small amounts ofalkali andhydro when necessary" to maintain alkaline reducing conditions as described in Example '1. The' skeins were then removed; oxidized; and-thou oughly soaped. The shade of'Dyeing #1 was dull and gray. The shades of the other dyeings were blue, bright, and stronger than #1, becoming stronger and brighter as the amount of cobalt salt present in the-bathwas increased; numbers-'7 and 8 being-'the'strongest and brightest'ofjtheset.

Example 3' A 5% dyeing with the blue vat dye oiExample 1 was made on cotton at atemperature ofabout 93 C. in addition to the .dye, thebathcontained 4 ouncesper gallon of sodiumhydroxidae ounces per gallon of sodium hydrosulfitezandJ/l ounce.

per gallon of cobaltous chloride. The dyeing procedure was the same as in Example 1 except that the dyeing time was only as long. In spite of the larger amount of alkaline and reducing agents, a bright blue shade wa's'obtained' with good color value. In a control dyeing under the same conditions in which the cobaltous chloride wasnot present, the shade was dull and gray.

Example 4 A 5%;dyeing ofthe orange dye, Color Index No. 1098, was made on cotton at a temperature of 93" C. The dye bath. contained in addition to the'dye, 4 oun'ces per'gallon of sodium hydroxide, 4 ounces per gallon of sodium hydrosulfite and /6' ounce per gallon of cobaltous chloride. The dyewas: reduced for one minute and the skein then introduced and dyed for 30 minutes at about 93 C. adding small amounts of sodium hydrosulfite and alkali as needed to maintain alkaline reducingiconditions'in the bath; The skein'was then removed; oxidized; and soaped; 'I'heresulting dyeinghad an excellent strong;.bright, orange shade.

A corresponding'dyeing made at th'easame time in'x exactly the same manner; except-thatn'oi cobaltous chloride. was 1 present,: was weaker; duller and; redderin. shade.

Example 5 A dye." bath was prepared with 0.4 part of commerical vat dye paste ofColor IndexNo: 1106;

12.5 partsiof 30 B sodium'hydroxide; BQO-parts of water, 4' parts sodium hydrosulfite, and 5 parts of a 5%. solution of cobaltouschloride. The'dyen was reduced. for 5 minutes at --95 C. anda scoured cotton skein amountingto 5 partswas en'-- ered and. dyed at the-same-temperatureforithe: same period-of"time-asused:.irr Example 3, small amounts of sodium hydroxide and'sodium hydrosulfite being added as necessary-to maintain the alkaline reducing conditions-asdescribed in con nection with Example 1.

After the dying, was complete, the; skein: was removed, oxidized and seeped: It was dyed. adeep strong blueshade; Awcorresponding dyeing under identical conditions but without cobaltous chloridesgave a muchduller andweaker shade.

Eicample '6 The: dye bath was prepared--with onepartof. commercial vat dyepaste Color Index'No. 1-101, 12.5 parts 30 B. sodium hydroxide, 390 partsiof= water, 4 parts ofsodium vhydrosulfiteand. 5-. parts of a5% solution of cobaltous chloride. Aftertheaddition of the hydrosulfite,:the':'dye wasreduced. at 93-94" C. and ascotton skein amounting.- to 20 parts, pretreated in a:- hotpine oil soap solution,

was then rinsedand entered intothe dye bath and. dyed at ill-93 C. until the-optimum shade was produced. The dye-bath was tested from time to. time as'in Example-,1, and: additional: sodium.

hydrosulfite added.v where required.

After the dyeing. was complete, the. cotton skein Was-removedwfrom" the bath; oxidizedinthe air for about 5 minutes, rinsed, oxidized in a warm acetic acid SOhltlOIlTOf hydrogenperoxide, again rinsed, soaped: at the boil in'a' 0.1% soap solution followed. by a a. final rinse and. air dried.

A controldyeing-was made-in the'same manner except no cobalt chloride was addedto thebath.

When the'shade-of the dyeing made in the pres ence; of the cobalt compoundwas compared. to that of. the-control-dyeing, the dyeing made inthe presenceofcobalt was-stronger, brighter, and

more 7 pleasing.

Example 7 The procedure of the preceding example was repeated, except that the vat dye 6,6'-dichloro- 4, l-dimethyl-2,2-thionaphthene indigo was used instead of the dye having Color Index No. 1101.

A control dyeing was prepared in the same manner, except the cobalt chloride was omitted from the dye bath.

The shade of the skein dyed in the dye bath containing the cobalt chloride was very much stronger and brighter than the control dyeing.

Example 8 The procedure of Example 6 was repeated excent the pentanthrimide dye of U. S. Patent 2,434,056 is used instead of the dye of Example 6. The shade of the skein dyed in the presence of the cobalt salt was noticeably stronger than the shade of the skein dyed in the control bath.

Example 9 A dye bath was prepared containing 100 parts of a 1% aqueous dispersion of a commercial paste of blue dye of Example 1, 12.5 parts of 30 B. sodium hydroxide, 290 parts of water, 4 parts of sodium hydrcsulfite, and 1 part of a wet filter cake of higher cobalt oxides obtained by filtering the dispersion prepared by adding 100 parts of an aqueous solution of sodium hypochlorite (10-15% available chlorine) to a mixture of 10 parts of hydrated cobalt acetate, 100 parts of water and 5 parts of 30 B. sodium hydroxide. The dye bath was reduced at 90-93 C.

An unbleached cotton skein, amounting to parts, which had been prewet in a dilute pine oil soap solution and rinsed was then introduced into the bath and dyed at 90-93 C. to good shade, the bath being tested frequently and small amounts of sodium hydroxide and sodium hydrosulfite added when needed to maintain alkaline reducing conditions in the bath at all times. A control dyeing was effected in the same manner except that no cobalt oxides were present in the bath.

The shade of the dyeing made in the presence of the higher cobalt oxides was an excellent blue showing that the vat dye had not decomposed at this high temperature; while the shade of the control dyeing was a dull gray color which could not possibly be substituted for the bright blue shade.

Example 10 The procedure of the preceding example was repeated, except the higher oxides of cobalt were replaced by 1 part of a powdered cobaltite product prepared by grinding the material obtained by fusing 10 parts of black cobalt oxide and 30 parts of sodium hydroxide gently until bubbling had ceased, then heating at a dull red heat for 2 hours with occasional stirring. The shade of the skein dyed in the bath containing this cobalt material was a bright blue shade when compared with the dull gray shade of the control dyeing.

Example 11 The procedure of the preceding example was repeated, except 1 part of the wet filter cake of cobalt sulfide which was precipitated by adding a solution of sodium sulfide to a solution of cobaltous chloride was used instead of the powdered cobaltite product of the preceding example.

A control dyeing was prepared in the same manner except the cobalt compound was omitted from the dye bath.

a dull gray.

6 i The shade of the cotton skein dyed in the presence of the cobalt sulfide was a strong bright blue, while the shade of the control dyeing was Example 12 Example 13 A dye bath was prepared with 1 part of the commercial paste of the blue dye of Example 1, 12.5 parts 30 Be. sodium hydroxide, 300 parts of water, 0.2 part of cobalt acetate and 4 parts of sodium hydrosulfite. The bath was reduced at -94" C. and an unbleached cotton skein, amounting to 20 parts, which had been thoroughly wet out in dilute pine oil soap solution and rinsed, was introduced into the bath and dyed to good shade at the same temperature. The bath was tested frequently with phenolphthalein and Vat Yellow G test papers, and small additions of sodium hydroxide and sodium hydrosulfite were made when needed to maintain alkaline reducing conditions in the bath.

After the dyeing was completed, the dyed skein was removed, air oxidized, followed by oxidation in a warm dilute acetic acid solution of hydrogen peroxide, rinsed, thoroughly soaped at the boil in a 0.1% soap solution, again rinsed and dried. The shade was a strong bright blue.

Example 14 The procedure of the preceding example was repeated, except 1 part of cobalt linoleate containing about 8.5% cobalt was used. The shade of the dyeing made in the presence of the cobalt linoleate was a bright blue, having excellent strength.

Example 15 The procedure of Example 13 was repeated, except 1 part of cobalt resinate was used instead of the cobalt acetate. Again the shade of the dyeing was a bright blue whereas the control dyeing prepared with no cobalt compound present was a dull dirty gray.

Example 16 The procedure of Example 13 was repeated, except 0.2 part of black cobalt oxide was used instead of cobalt acetate. The shade of the dyeing prepared in the presence of the cobalt oxide was a good blue while the shade of the control dyeing prepared in the absence of cobalt was dull and gray.

Example 17 The procedure of the preceding example was repeated, except 5 parts of cobalt metallic powder were used instead of the cobalt oxide and the results were generally similar to those in the preceding example.

Iclaim:

1. In a process of dyeing textile fibers from a vat dye bath containing at least one vat dye subject to damage at elevated temperatures, alkali and sufiicient sodium hydrosulfite to maintain reduction of the vat dyestuff, said dye bath being maintained at high temperatures for long periods of time, the temperatures being sufiici'ently elevated and the timesufliciently longso that vat dyestufis subject to damage are ad-- versely effected thereby, the improvement which comprises maintaining in said dye bath an amount of ionized cobalt compound corresponding to at least of an ounce of cobalt-per gallonof dye bath.

2. A method according to claim 1 in which the dyestufi is an anthraquinone dihydroazine;

3. A method according to claim 2 in which the cobalt compound is a cobaltous salt.

4. A method according to claim 3 in which-the cobaltous salt is cobaltous chloride.

5. A method according to claim 1 in which the amount of the cobalt compound is to /3 15 um of an ounce per gallon of dye bath;

6. A method according to claim 5 in which the dyestuff: is anthraquinone dihydroazine.

7. A: method according to claim 6 in which the cobalt compound is cobaltous salt.

8. A method according'to claim '7 in which the cobaltous salt is cobaltous chloride.

Refeiehcs Cited in the file Of this atent UNITED STATES PATENTS Number Name Date 2,06%92'7' Kern Jan. 19, 1937 2,067,928 Kern .-c Jan. 19, 1937 FOREIGN PATENTS Country Date 534,085 Great-Britain Feb. 2'7, 1941 

1. IN A PROCESS OF DYEING TEXTILE FIBERS FROM A VAT DYE BATH CONTAINING AT LEAST ONE VAT DYE SUBJECT TO DAMAGE AT ELEVATED TEMPERATURES, ALKALI AND SUFFICIENT SODIUM HYDROSULFITE TO MAINTAIN REDUCTION OF THE VAT DYSTUFF, SAID DYE BATH BEING MAINTAINED AT HIGH TEMPERATURES FOR LONG PERIODS OF TIME, THE TEMPERATURES BEING SUFFICIENTLY ELEVATED AND THE TIME SUFFICIENTLY LONG SO THAT VAT DYESTUFFS SUBJECT TO DAMAGE ARE ADVERSELY EFFECTED THEREBY, THE IMPROVEMENT WHICH COMPRISES MAINTAINING IN SAID DYE BATH AN AMOUNT OF IONIZED COBALT COMPOUND CORRESPONDING TO AT LEAST 1/240 OF AN OUNCE OF COBALT PER GALLON OF DYE BATH. 